/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package qunar.tc.bistoury.instrument.client.spring.el;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.ParseException;

/**
 * Miscellaneous utility methods for number conversion and parsing.
 * Mainly for internal use within the framework; consider Jakarta's
 * Commons Lang for a more comprehensive suite of string utilities.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @since 1.1.2
 */
public abstract class NumberUtils {

    /**
     * Convert the given number into an instance of the given target class.
     *
     * @param number      the number to convert
     * @param targetClass the target class to convert to
     * @return the converted number
     * @throws IllegalArgumentException if the target class is not supported
     *                                  (i.e. not a standard Number subclass as included in the JDK)
     * @see Byte
     * @see Short
     * @see Integer
     * @see Long
     * @see BigInteger
     * @see Float
     * @see Double
     * @see BigDecimal
     */
    @SuppressWarnings("unchecked")
    public static <T extends Number> T convertNumberToTargetClass(Number number, Class<T> targetClass)
            throws IllegalArgumentException {

        Assert.notNull(number, "Number must not be null");
        Assert.notNull(targetClass, "Target class must not be null");

        if (targetClass.isInstance(number)) {
            return (T) number;
        } else if (targetClass.equals(Byte.class)) {
            long value = number.longValue();
            if (value < Byte.MIN_VALUE || value > Byte.MAX_VALUE) {
                raiseOverflowException(number, targetClass);
            }
            return (T) new Byte(number.byteValue());
        } else if (targetClass.equals(Short.class)) {
            long value = number.longValue();
            if (value < Short.MIN_VALUE || value > Short.MAX_VALUE) {
                raiseOverflowException(number, targetClass);
            }
            return (T) new Short(number.shortValue());
        } else if (targetClass.equals(Integer.class)) {
            long value = number.longValue();
            if (value < Integer.MIN_VALUE || value > Integer.MAX_VALUE) {
                raiseOverflowException(number, targetClass);
            }
            return (T) new Integer(number.intValue());
        } else if (targetClass.equals(Long.class)) {
            return (T) new Long(number.longValue());
        } else if (targetClass.equals(BigInteger.class)) {
            if (number instanceof BigDecimal) {
                // do not lose precision - use BigDecimal's own conversion
                return (T) ((BigDecimal) number).toBigInteger();
            } else {
                // original value is not a Big* number - use standard long conversion
                return (T) BigInteger.valueOf(number.longValue());
            }
        } else if (targetClass.equals(Float.class)) {
            return (T) new Float(number.floatValue());
        } else if (targetClass.equals(Double.class)) {
            return (T) new Double(number.doubleValue());
        } else if (targetClass.equals(BigDecimal.class)) {
            // always use BigDecimal(String) here to avoid unpredictability of BigDecimal(double)
            // (see BigDecimal javadoc for details)
            return (T) new BigDecimal(number.toString());
        } else {
            throw new IllegalArgumentException("Could not convert number [" + number + "] of type [" +
                    number.getClass().getName() + "] to unknown target class [" + targetClass.getName() + "]");
        }
    }

    /**
     * Raise an overflow exception for the given number and target class.
     *
     * @param number      the number we tried to convert
     * @param targetClass the target class we tried to convert to
     */
    private static void raiseOverflowException(Number number, Class targetClass) {
        throw new IllegalArgumentException("Could not convert number [" + number + "] of type [" +
                number.getClass().getName() + "] to target class [" + targetClass.getName() + "]: overflow");
    }

    /**
     * Parse the given text into a number instance of the given target class,
     * using the corresponding {@code decode} / {@code valueOf} methods.
     * <p>Trims the input {@code String} before attempting to parse the number.
     * Supports numbers in hex format (with leading "0x", "0X" or "#") as well.
     *
     * @param text        the text to convert
     * @param targetClass the target class to parse into
     * @return the parsed number
     * @throws IllegalArgumentException if the target class is not supported
     *                                  (i.e. not a standard Number subclass as included in the JDK)
     * @see Byte#decode
     * @see Short#decode
     * @see Integer#decode
     * @see Long#decode
     * @see #decodeBigInteger(String)
     * @see Float#valueOf
     * @see Double#valueOf
     * @see BigDecimal#BigDecimal(String)
     */
    @SuppressWarnings("unchecked")
    public static <T extends Number> T parseNumber(String text, Class<T> targetClass) {
        Assert.notNull(text, "Text must not be null");
        Assert.notNull(targetClass, "Target class must not be null");
        String trimmed = StringUtils.trimAllWhitespace(text);

        if (targetClass.equals(Byte.class)) {
            return (T) (isHexNumber(trimmed) ? Byte.decode(trimmed) : Byte.valueOf(trimmed));
        } else if (targetClass.equals(Short.class)) {
            return (T) (isHexNumber(trimmed) ? Short.decode(trimmed) : Short.valueOf(trimmed));
        } else if (targetClass.equals(Integer.class)) {
            return (T) (isHexNumber(trimmed) ? Integer.decode(trimmed) : Integer.valueOf(trimmed));
        } else if (targetClass.equals(Long.class)) {
            return (T) (isHexNumber(trimmed) ? Long.decode(trimmed) : Long.valueOf(trimmed));
        } else if (targetClass.equals(BigInteger.class)) {
            return (T) (isHexNumber(trimmed) ? decodeBigInteger(trimmed) : new BigInteger(trimmed));
        } else if (targetClass.equals(Float.class)) {
            return (T) Float.valueOf(trimmed);
        } else if (targetClass.equals(Double.class)) {
            return (T) Double.valueOf(trimmed);
        } else if (targetClass.equals(BigDecimal.class) || targetClass.equals(Number.class)) {
            return (T) new BigDecimal(trimmed);
        } else {
            throw new IllegalArgumentException(
                    "Cannot convert String [" + text + "] to target class [" + targetClass.getName() + "]");
        }
    }

    /**
     * Parse the given text into a number instance of the given target class,
     * using the given NumberFormat. Trims the input {@code String}
     * before attempting to parse the number.
     *
     * @param text         the text to convert
     * @param targetClass  the target class to parse into
     * @param numberFormat the NumberFormat to use for parsing (if {@code null},
     *                     this method falls back to {@code parseNumber(String, Class)})
     * @return the parsed number
     * @throws IllegalArgumentException if the target class is not supported
     *                                  (i.e. not a standard Number subclass as included in the JDK)
     * @see NumberFormat#parse
     * @see #convertNumberToTargetClass
     * @see #parseNumber(String, Class)
     */
    public static <T extends Number> T parseNumber(String text, Class<T> targetClass, NumberFormat numberFormat) {
        if (numberFormat != null) {
            Assert.notNull(text, "Text must not be null");
            Assert.notNull(targetClass, "Target class must not be null");
            DecimalFormat decimalFormat = null;
            boolean resetBigDecimal = false;
            if (numberFormat instanceof DecimalFormat) {
                decimalFormat = (DecimalFormat) numberFormat;
                if (BigDecimal.class.equals(targetClass) && !decimalFormat.isParseBigDecimal()) {
                    decimalFormat.setParseBigDecimal(true);
                    resetBigDecimal = true;
                }
            }
            try {
                Number number = numberFormat.parse(StringUtils.trimAllWhitespace(text));
                return convertNumberToTargetClass(number, targetClass);
            } catch (ParseException ex) {
                throw new IllegalArgumentException("Could not parse number: " + ex.getMessage());
            } finally {
                if (resetBigDecimal) {
                    decimalFormat.setParseBigDecimal(false);
                }
            }
        } else {
            return parseNumber(text, targetClass);
        }
    }

    /**
     * Determine whether the given value String indicates a hex number, i.e. needs to be
     * passed into {@code Integer.decode} instead of {@code Integer.valueOf} (etc).
     */
    private static boolean isHexNumber(String value) {
        int index = (value.startsWith("-") ? 1 : 0);
        return (value.startsWith("0x", index) || value.startsWith("0X", index) || value.startsWith("#", index));
    }

    /**
     * Decode a {@link BigInteger} from a {@link String} value.
     * Supports decimal, hex and octal notation.
     *
     * @see BigInteger#BigInteger(String, int)
     */
    private static BigInteger decodeBigInteger(String value) {
        int radix = 10;
        int index = 0;
        boolean negative = false;

        // Handle minus sign, if present.
        if (value.startsWith("-")) {
            negative = true;
            index++;
        }

        // Handle radix specifier, if present.
        if (value.startsWith("0x", index) || value.startsWith("0X", index)) {
            index += 2;
            radix = 16;
        } else if (value.startsWith("#", index)) {
            index++;
            radix = 16;
        } else if (value.startsWith("0", index) && value.length() > 1 + index) {
            index++;
            radix = 8;
        }

        BigInteger result = new BigInteger(value.substring(index), radix);
        return (negative ? result.negate() : result);
    }

}
